Polymeric Nanoparticles as Oral and Intranasal Peptide Vaccine Delivery Systems: The Role of Shape and Conjugation.

Mucosal vaccines are highly attractive due to high patient compliance and their suitability for mass immunizations. However, all currently licensed mucosal vaccines are composed of attenuated/inactive whole microbes, which are associated with a variety of safety concerns. In contrast, modern subunit vaccines use minimal pathogenic components (antigens) that are safe but typically poorly immunogenic when delivered via mucosal administration. In this study, we demonstrated the utility of various functional polymer-based nanostructures as vaccine carriers. A Group A Streptococcus (GAS)-derived peptide antigen (PJ8) was selected in light of the recent global spread of invasive GAS infection. The vaccine candidates were prepared by either conjugation or physical mixing of PJ8 with rod-, sphere-, worm-, and tadpole-shaped polymeric nanoparticles. The roles of nanoparticle shape and antigen conjugation in vaccine immunogenicity were demonstrated through the comparison of three distinct immunization pathways (subcutaneous, intranasal, and oral). No additional adjuvant or carrier was required to induce bactericidal immune responses even upon oral vaccine administration.

Polyacrylate-GnRH Peptide Conjugate as an Oral Contraceptive Vaccine Candidate.

Contraceptive vaccines are designed to elicit immune responses against major components of animal reproductive systems. These vaccines, which are most commonly administered via injection, typically target gonadotropin-releasing hormone (GnRH). However, the need to restrain animals for treatment limits the field applications of injectable vaccines. Oral administration would broaden vaccine applicability. We explored contraceptive vaccine candidates composed of GnRH peptide hormone, universal T helper PADRE (P), and a poly(methylacrylate) (PMA)-based delivery system. When self-assembled into nanoparticles, PMA-P-GnRH induced the production of high IgG titers after subcutaneous and oral administration in mice. PADRE was then replaced with pig T helper derived from the swine flu virus, and the vaccine was tested in pigs. High levels of systemic antibodies were produced in pigs after both injection and oral administration of the vaccine. In conclusion, we developed a simple peptide-polymer conjugate that shows promise as an effective, adjuvant-free, oral GnRH-based contraceptive vaccine.